The present invention relates to a device for automatic engagement of printing sets under pressure in printing machines with paper reversers.
In printing machines, the automatic engagement of impression pressure on the separate printing sets can be controlled depending on the paper transfer by the machine. The printing machine can be provided with a paper reverser, which makes it possible to print on both sides of the sheet. Moreover, it is necessary that the mechanism for engaging the printing sets under pressure be synchronized with the paper reverser without any intervention of the operator.
For the automatic engagement of printing sets under pressure, various relay or electronic circuits are used. However, it is necessary to distribute about the printing machine paper presence scanners or swivelling stage scanners for paper reversers.
The disadvantage of the circuits hitherto used is the necessity of arranging paper presence scanners about the machine, particularly on the paper reverser where it is necessary to check the correct position of the paper after it is handled by the paper reverser.
The above disadvantages are mitigated by the present invention where the paper feeding scanner, together with the scanner for checking the angle of displacement of the machine cylinders are connected, via a first coincidence gate, to the input of the first memory. The output of the first memory is connected to the serial input of the first shift register. To the clock pulse input of the first shift register is connected a pulse scanner for scanning pulses which are synchronous with the revolutions of the printing machine parts upstream of the paper reverser. To the first storage location of the first shift register is connected the first circuit for engaging printing sets under pressure. The other storage locations of the first shift register, which coincide with the position of the paper reverser within the system of the printing machine printing sets and transfer drums, are connected to the serial input of the second shift register. The clock pulse input of the second shift register is connected to a pulse sensor for sensing pulses synchronous with the revolutions of the machine parts downstream of the paper reverser. To the storage locations of the second shift register, which correspond to the number of revolutions since the inlet of the paper sheet, a second circuit for engaging the printing sets under pressure is connected.
The present invention makes possible that, upon handling of paper by the paper reverser, the operator need not perform any readjustment or checking.